The Study On The Gel-like Network Of Hyperconcentrated Cohesive Sediment Suspensions

Colloidal aggregation phenomena are often encountered in cohesive sediment suspensions in which aggregation results from interactions between fine particles. This paper presented the preliminary research results on gel-like network formed in hyperconcentrated cohesive sediment suspensions. To understand the properties of gel-like network of hyperconcentrated cohesive sediment suspensions, previous works were summarized and a series of settling experiments were carried out. Observations on experiments showed that the settling processes consist of three different stages namely network forming, collective settling and compaction process. During the collective settling stage the settling curves of the gel-like network were close to linearity, and the light fluctuations of the setting velocity appeared continually. During the compaction process the settling curves were nonlinearly, and no fluctuation of the setting velocity was observed. Experimental results showed that the diameter of particles, initial sediment concentration, the valence of cation and electrolyte strength added to the suspensions had all effects on settling processes. Combining the fractal theory and DLVO theory, a mechanism was put forth to interpret the settling behaviors observed. And the collision efficiency of fine cohesive sediments in suspensions was discussed as well.It was indicated that the critical condition of settling of a gel-like network in cohesive sediment suspensions depended on both the structure and interaction between particles of clusters. Based on the fractal theory and DLVO theory a method to estimate the critical initial sediment concentration for formation of initial gel-like networks under various electrolyte conditions was proposed, in which not only structure of gel-like network but also effects of electrolyte strength and valence of cation were included. A fractal demension of 2.15 and a magnitude of nN of interparticle force were obtained for the clusters. The critical concentration is about 100~200kg/m3 (about 3.8~7.7% in volume fraction), which agrees with the results put forward by other methods in order of magnitude.Finally, a preliminary discussion on the compaction model of gel-like network was made. The results are reasonable and much more researches are required in this field.